Heavy duty diesel internal combustion engines mounted on motor-driven vehicles, constructions machines and power generators are generally driven using gas oil or heavy oil (which is a fuel having a sulfur content of approximately 0.05 wt. % or more). Most lubricating oils for the diesel engines have a sulfur content of approximately 0.3 to 0.7 weight percent, a sulfated ash content of approximately 1.3 to 2.0 weight percent, and a phosphorus content of approximately 0.1 to 0.13 weight percent.
In order to reduce air pollution, vehicle manufacturers and petroleum companies are interested in developing lubricating oil systems that have low emissions and better fuel economy for heavy duty diesel engines. Environmental pollution caused by emissions from diesel engines may comprise particulates and carbon oxides, sulfur oxides and nitrogen oxides. Diesel engine manufacturers have started to equip diesel engines with exhaust after-treatment devices containing particulate filters, oxidation catalysts and reduction catalysts to obviate environmental problems.
Both the fuel and the lubricating oil used to lubricate diesel engines contribute to particulates and oxides found in emissions from diesel engines. A major concern is sulfated ash derived from the salts of alkali and alkaline earth metal detergent additives in lubricating oil. The non-combustible ash deposits in diesel engines become trapped in the channels of diesel engine exhaust gas particulate filters. Conventional lubricating oils used in diesel engines are also high in sulfur content, which originates in the additive components and the base oil. Sulfur in diesel fuels is converted to sulfuric acid and sulfates which emigrate to the exhaust gas cleaning devices and directly contribute to the particulates that clog the particulate filters in heavy duty diesel engine vehicles equipped with them. Sulfuric acid may also indirectly contribute to clogging the particulate filters by wetting the particulates, thus adding to their mass. The sulfuric acid and the sulfates also poison the oxidation catalysts in the exhaust gas cleaning devices which may also result in failure to meet emission requirements. Thus, for continued functioning of these particulate traps and oxidation catalysts, it is essential that the sulfur and sulfated ash content in the lubricating oil is lowered considerably compared to the conventional diesel engine lubricating oils.
Anti-wear and anti-oxidants, such as zinc di-alkyl di-thiophosphates, also contribute to reduction in the activity of the oxidation catalysts. Increased phosphorus levels in the lubricating oil enhance deactivation of the oxidation catalysts used in exhaust gas cleaning devices. Therefore, there is a need to decrease the phosphorus content in the lubricating oil to keep the oxidation catalysts from deterioration. Furthermore, the zinc contributes to the sulfated ash which cogs the particulate filters in the exhaust gas cleaning devices.
A number of patents and patent applications have discussed methods for reducing particulate emissions and low sulfur, low sulfated ash and low phosphorus lubricating oil compositions, but none have disclosed a low emission lubricating oil of the present invention for diesel engines. Canadian Patent No. 810120 discloses a lubricating oil composition comprising the reaction product obtained by the neutralization with an alkaline earth metal oxide or hydroxide of a sulfurized alkyl phenol in admixture with a Mannich base reacted with carbon dioxide.
U.S. Pat. No. 5,102,566 discloses a low sulfated ash lubricating oil composition which comprises a base oil, at least about 2 weight percent of an ashless nitrogen- or ester-containing dispersant, an oil-soluble antioxidant material, and an oil soluble di-hydrocarbyl di-thiophosphate anti-wear material, and which has a total sulfated ash level of 0.01 to 0.6 weight percent and a weight ratio of total sulfated ash and the dispersant in the range of 0.01:1 to 0.2:2.
U.S. Pat. Nos. 5,486,300 and 5,490,945 disclose a lubricating oil composition comprising a major amount of an oil of lubricating viscosity; and (A) an amount of at least one alkali metal overbased salt of an acidic organic compound sufficient to provide at least about 0.005 equivalents of alkali metal per 100 grams of lubricating composition; (B) at least about 1.13% by weight of at least one dispersant; (C) at least one metal di-hydrocarbyl di-thiophosphate; and (D) at least one anti-oxidant, provided that the lubricating oil composition is free of calcium overbased sulfonate provided that the composition contains less than about 0.08% by weight calcium; and provided that (C) and (D) are not the same.
U.S. Pat. Nos. 5,562,864 and 5,614,480 disclose a lubricating oil composition which comprises a major amount of an oil of lubricating viscosity and (A) at least about 1% by weight of at least one carboxylic derivative composition produced by reacting (A-1) at least one substituted succinic acylating agent containing at least 50 carbon atoms in the substituent with (A-2) from about 0.5 equivalents up to about 2 moles per equivalents of acylating agent (A-1), or at least one amine compound characterized by the presence within its structure of at least one HN<group; and (B) an amount of at least one alkali metal overbased salt of a carboxylic acid or a mixture of a carboxylic acid and an organic sulfonic acid sufficient to provide at least about 0.002 equivalent of alkali metal per 100 grams of the lubricating oil composition provided that when the alkali metal salt comprises a mixture of overbased alkali metal salts of hydrocarbyl-substituted carboxylic acids and a hydrocarbyl-substituted sulfonic acid, then the carboxylic acid comprises more than 50% of the acid equivalents of the mixture; and either; (C-1) at least one magnesium overbased salt of an acidic organic compound provided that the lubricating oil composition is free of calcium overbased salts of acidic organic compounds; or (C-2) at least one calcium overbased salt of an acidic organic compounds provided that the lubricating composition is free of magnesium overbased salts of acidic organic compounds.
U.S. Pat. No. 5,726,133 discloses a low ash natural gas engine oil which contains an additive package including a particular combination of detergents and also containing other standard additives such as dispersants, anti-oxidants, anti-wear agents, metal deactivators, anti-foamants and pour point depressants and viscosity index improvers. The low ash natural gas engine oil exhibits reduced deposit formation and enhanced resistance to oil oxidation and nitration.
U.S. Pat. No. 6,140,282 discloses a long life lubricating oil as evidenced by a reduction in viscosity increase, oxidation and nitration, comprising a major amount of a base oil of lubricating viscosity and a minor amount of a mixture of high TBN, medium TBN and low/neutral TBN detergents which in the metal salicylate detergents is at least one of the medium or low/neutral TBN detergents.
U.S. Pat. No. 6,159,911 discloses a diesel engine oil composition containing a lube oil base and one or more metallic detergents-dispersants selected from among a perbasic alkaline earth metal sulfonate, phenolate and salicylate. The total phosphorus content of the composition is suppressed to 100 parts per million by weight or less, to thereby provide diesel engine oil compositions having oxidation stability and wear resistance.
U.S. Pat. No. 6,162,770 discloses an un-sulfurized, alkali metal-free, detergent-dispersant composition having from about 40% to 60% alkylphenol, from 10% to 40% alkaline earth alkylphenol, and from 20% to 40% alkaline earth single aromatic-ring alkylsalicylate. This composition may have an alkaline earth double aromatic-ring salicylates as long as the mole ratio of single-ring alkylsalicylate to double aromatic ring alkylsalicylate is at least 8:1.
U.S. Pat. No. 6,277,794 discloses a marine diesel lubricant composition having a TBN of at least 10 and preferably a VI of at least 90, comprise a major amount of oil of lubricating viscosity, and admixed therewith, minor amounts of an ashless anti-wear additive and a metal detergent in the form of (i) an overbased metal detergent having a TBN of at least 300, more preferably at least 400, and comprising a surfactant system derived from at least two surfactants, and/or (ii) a metal detergent other than (i); provided that, if detergent (ii) is present, the composition does not contain a minor amount of an extreme pressure additive, being up to 5.0 mass percent on the total mass of the composition.
U.S. Pat. Nos. 6,331,510 and 6,610,637 disclose a lubricant containing (a) a synthetic base oil composition having an overall kinematic viscosity of at least about 4.8×10−6 m2/s (4.8 cSt) at 100° C. and a viscosity index of at least 110; (b) a dispersant-viscosity modifier; and (c) a sulfur-free functionalized hydrocarbyl-substituted phenol detergent provides improved valve train wear, with longer drain intervals, to heavy duty diesel engines.
U.S. Pat. No. 6,569,818 discloses a lubricating oil composition having a low phosphorus content of 0.01 to 0.1 weight percent, and a sulfated ash of 0.1 to 1.0 weight percent, which is composed of a (a) major amount of mineral base oil having a low sulfur content of at most 0.1 weight percent; (b) an ashless alkenyl or alkyl-succinimide dispersant; (c) a metal-containing detergent (non-sulfurized alkali metal or alkaline earth metal salt of an alkylsalicylic acid and/or non-sulfurized alkali metal or alkaline earth metal salt of an alkyl phenol having a Mannich base structure; (d) zinc di-alkyl di-thiophosphate; (e) an oxidation inhibitor (phenol compound and/or amine compound) and wherein the sulfur content is 0.01 to 0.3 weight percent. The lubricating oil composition shows good high temperature detergency notwithstanding its low sulfur, phosphorus and sulfated ash content, and is favorably employable in diesel engines using fuel of a low sulfur content.
U.S. Pat. No. 6,730,638 discloses a lubricating oil for internal combustion engines especially useful with fuels having less than 350 parts per million sulfur comprises a lubricating oil basestock, a boron containing ashless dispersant, a molybdenum containing friction reduction agent, a metal type detergent and zinc di-thiophosphate.
U.S. Pat. No. 6,784,143 discloses the use of a minor amount of a detergent composition comprising one or more metal detergents which comprises metal salts of organic acids, wherein the detergent composition comprises more than 50 mole percent, based on the moles of the metal salts of organic acids in the detergent composition, of: (I) a metal salt of an aromatic carboxylic acid, or (II) a metal salt of a phenol, or (III) both a metal salt of an aromatic carboxylic acid and a metal salt of a phenol, in a lubricating oil composition for improving oxidation resistance of the lubricating oil composition, wherein the amount of phosphorus and sulfur in the oil composition is less than 0.09 mass % and at the most 0.5 mass % respectively, based on the mass of the oil composition. It has also been found that a detergent composition comprising more than 50 mole % of a metal salt of an aromatic carboxylic acid improves the reduction in wear in an engine.
European Patent Application No. 01201752.1 (Publication No. EP 1 256 619 A1) deemed withdrawn as of Mar. 5, 2005, and U.S. patent application Ser. No. 10/142,513 (Publication No. US 2003/0096716 A1) disclose a lubricating oil composition comprising: (A) an oil of lubricating viscosity, in a major amount and added thereto: (B) a detergent composition comprising one or more metal detergents which comprises metal salts or organic acids, in a minor amount, wherein the detergent composition comprises more than 50 mole percent of a metal salt of an aromatic carboxylic acid, based on the moles of the metal salts of organic acids in the detergent composition, and (C) one or more co-additives, in a minor amount; wherein the total amounts of phosphorus and sulfur derived from (B) or (C) or both (B) and (C) are less than 0.1 mass p % of phosphorus and at the most 0.5 mass % of sulfur, based on the mass of the oil composition. It has been found that a detergent composition comprising more than 50 mole % of a metal salt of an aromatic carboxylic acid improves the reduction in wear in an engine.
U.S. patent application Ser. No. 10/430,594 (Publication No. US 2003/0216266 A1) discloses a lubricating oil composition employable in combination with a low sulfur content fuel oil is preferably composed of a base oil having a sulfur content of at most 0.2 weight percent, an ashless dispersant comprising an alkenyl- or alkyl-succinimide or derivative thereof, a metal-containing detergent containing an organic acid metal salt, a zinc di-alkyl di-thiophosphate, a zinc di-alkylaryl di-thiophosphate, and an oxidation inhibitor selected from a group consisting of a phenol compound, an amine compound, and a molybdenum-containing compound, wherein a ratio of the phosphorus content of the zinc di-alkyl di-thiophosphate to the phosphorus content of the zinc di-alkylaryl di-thiophosphate is in the range of 20:1 to 2:1.
U.S. patent application Ser. No. 10/344,390 (Publication No. US 2004/0106527 A1) discloses a lubricating oil composition used in conjunction with a gasoline fuel having a sulfur content of less than 10 parts per million by weight, characterized in that said oil composition has a phosphorus content of no more than 0.05 percent by weight.
International Publication No. WO 2004/046283 A1 discloses the use of lubricating oils with low sulfur content in combination with a low sulfur fuel to reduce particulate emissions of a diesel engine equipped with a particulate trap.
U.S. patent application Ser. No. 10/630,026 (Publication No. US 2005/0026791 A1) discloses a low sulfur, low ash, and low phosphorus lubricant additive package comprising at one amine salt of a di-alkyl mono-thiophosphate. Further, the patent application discloses lubricating oils based on the lubricant additive package and methods of use.